The Supreme Court decision overturning a new federal statute outlawing flag desecration instantly revived a rancorous and emotional debate on Capitol Hill yesterday and set up a what is likely to be a nasty political fight as lawmakers prepare for the fall elections.

Lawmakers in both the House and Senate took steps yesterday that will lead to speedy consideration of a flag-burning amendment to the Constitution, probably before the July 4 recess. The House Judiciary Committee is to begin work on an amendment next week, and floor action is expected within two to four weeks.

The court's 5 to 4 decision put the contentious issue back on the congressional agenda just as the 1990 campaign season is heating up, whetting the appetite of Republican political operatives hungry for "values" issues they can use against the Democratic majorities in the House and Senate. Republicans have been in the forefront in pushing for an amendment while key Democratic congressional leaders are committed to opposing an amendment that would alter the Bill of Rights.

However, neither supporters nor opponents of an amendment appeared confident of the outcome in a showdown over the issue with both sides predicting the issue would hinge on the public's response to the debate. A Washington Post-ABC poll last year showed a strong majority of voters favored congressional action to protect the flag, but by a 2 to 1 margin voters said they preferred a statute over a constitutional amendment to achieve that goal. It was not clear how yesterday's decision overturning the federal statute would affect public sentiment toward an amendment.

"It's not going to be easy to get a two-thirds vote of the House," predicted Rep. G.V. "Sonny" Montgomery (D-Miss.), a supporter of an amendment.

Despite these uncertainties, Republicans yesterday eagerly anticipated how the issue will play this fall while Democrats wanly warned against playing politics with the flag.

A vote against a constitutional amendment, said Senate Minority Leader Robert J. Dole (R-Kan.), "would make a pretty good 30-second spot" by a lawmaker's opponent in the fall.

"Democrats are definitely not going to get a free ride on this," added Edward J. Rollins, co-chairman of the GOP's House campaign committee. "Defining values is very, very important."

Democratic Party chairman Ronald H. Brown sought to depoliticize the issue, declaring that "those who seek political advantage from the flag and the Bill of Rights slander the memory of every man or woman who fought for this land."

Republican congressional leaders said yesterday that the court's decision validated their arguments of last year that the only way to protect the nation's symbol is through a constitutional amendment, a view that Democratic leaders had finessed by passage of the statute that was overturned yesterday.

"There is no quick fix on this issue," said House Minority Leader Robert H. Michel (R-Ill.). "Either we amend the Constitution -- as grave and complicated an undertaking as that is -- or else we let the decision stand."

Both Michel and Dole have introduced identical proposed amendments that would empower Congress and the states to "prohibit the physical desecration of the flag of the United States." To be approved, the amendment would have to be supported by two-thirds of the House and Senate and then ratified by 38 of the 50 state legislatures.

The upcoming battle over a flag-burning amendment will be a key test of the leadership abilities of House Speaker Thomas S. Foley (D-Wash.) and Senate Majority Leader George J. Mitchell (D-Maine), both of whom oppose tampering with the First Amendment.

A White House official said President Bush is considering whether to escalate the issue politically, with administration planners eyeing two upcoming events to use as backdrops. One is an upcoming photo opportunity with the sculptor of the Iwo Jima Memorial statue; the other is Flag Day on Thursday.

Administration officials recognize the immediate emotional punch of the issue, but are not sure about its staying power. "The question is how quickly the attention grabs in the states to get it ratified," one official said.

Staff writer Dan Balz contributed to this report.